It is known that an internal combustion engine of a motor vehicle may be equipped with an aftertreatment system designed to change the composition of the exhaust gas in order to reduce the combustion by-products in the exhaust gas. Some aftertreatment systems may include a particulate filter, for example a Diesel particulate filter (DPF) designed to trap diesel particulate matter or soot contained in the exhaust gas.
During the lifetime of the DPF, the efficiency of this component may be monitored using a differential pressure sensor suitable to sense the differential pressure of the exhaust gas upstream of the DPF and downstream of the DPF. In particular, when a measured differential pressure becomes lower than a threshold value thereof, DPF may be detected as inefficient or, in other words, unsuitable to efficiently trap the soot matter and a malfunctioning of the DPF may be identified.
Generally, the differential pressure sensor is connected with two sensing points, the first located upstream of the DPF and the second located downstream of the DPF, by means of respective pipes. It is observed that, if a disconnection of the pipe connecting the differential pressure sensor with the second sensing point occurs, the measured differential pressure is always higher than the threshold value and, therefore, even if the DPF does not efficiently trap the soot matter, the malfunctioning of the DPF cannot be identified.
In most internal combustion engines a disconnection of the pipes is a rare event, caused in general by a tampering or a wrong service repair, but when the aftertreatment system layout of the ICE is equipped with an exhaust back pressure valve having an exhaust brake function, the possibility to observe disconnections, in particular of the pipe connecting the differential pressure sensor with the second sensing point located downstream of the DPF, increases, also during the ICE working conditions.
As a matter of fact the closure of the exhaust back pressure valve during the ICE working conditions may stress the pipe connections, in particular of the pipe connecting the differential pressure sensor with the second sensing point, due to the increasing pressure so-called back pressure) in the aftertreatment system caused by the closure of the exhaust back pressure valve.